12.
Earthquakes as a hazard <ul><li>Estimated > 8 million killed in earthquakes during last millennium </li></ul><ul><li>2 million deaths in 20 th century </li></ul><ul><li>1990-99 cost US$215 billion </li></ul><ul><li>Over 40 countries are under threat from major destructive quakes </li></ul><ul><li>Over 100 a year have potential for serious destruction (> M = 6) </li></ul>Source: USGS Introduction to Seismology-KFUPM

13.
Some notable earthquakes in history Source: Hazard Research Center Introduction to Seismology-KFUPM

21.
<ul><li>In general terms: </li></ul>estimate hazard - forecasting , time distribution zone or macrozone - space distribution microzone - local fluctuations  define design earthquakes select time histories (  seismograms) what is the maximum earthquake? what is the maximum loading during EQ? What is the lifetime of structure? What is design spectra like? what is the maximum credible loading? Introduction to Seismology-KFUPM

22.
Forecasting earthquakes <ul><li>Forecasting is not prediction </li></ul><ul><ul><li>less precise </li></ul></ul><ul><ul><li>based upon analysis of earthquake return periods rather than identification of pre-cursor y signs </li></ul></ul><ul><li>Active faults or fault segments do not rupture in a random manner </li></ul><ul><ul><li>they have characteristic return periods (or at least return period envelopes ) </li></ul></ul><ul><ul><li>these reflect strain accumulation along the fault and the capacity of the fault to resist strain up to a given characteristic point - for that fault or fault segment </li></ul></ul><ul><li>There are complications : </li></ul><ul><ul><li>Rupture will not occur according to a rigid timetable - there is a return period envelope rather than specific date </li></ul></ul><ul><ul><li>Strain may be released by one large quake or a number of smaller ones (e.g. Marmara Sea south of Istanbul) </li></ul></ul><ul><ul><li>this has implications for risk assessment </li></ul></ul>Introduction to Seismology-KFUPM Source

23.
The Seismic Gap concept <ul><li>Defined as an area in an earthquake-prone region where there has been a below average level of seismic energy release </li></ul><ul><li>The 1989 Loma Prieta quake filled a gap that had been aseismic since 1906 </li></ul><ul><li>Other gaps exist in </li></ul><ul><ul><li>Aleutian arc (Alaska) </li></ul></ul><ul><ul><li>south of Istanbul </li></ul></ul><ul><ul><li>Tokyo </li></ul></ul><ul><ul><li>southern California </li></ul></ul>Istanbul seismic gap Introduction to Seismology-KFUPM Source